VP6 from porcine rotavirus strain CN86: amino acid sequence divergence with conservation of subgroup II specificity.

A porcine rotavirus strain, CN86, originally isolated from rotavirus-infected piglets in Argentina, has been shown to possess unique characteristics. It was the first animal strain described to be antigenically related to human serotype G1 and the standard counterpart of another porcine strain showing rearrangement of genome segment 11. Owing to these features, molecular characterization of this virus seemed relevant. The gene encoding the major inner capsid protein, VP6, was cloned and its nucleotide sequence was determined. Comparative analysis of the deduced amino acid sequence of CN86 VP6 with those representing the four different subgroups showed that it is more closely related to subgroup II human Wa and porcine Gottfried strains, albeit to a lesser extent than they are to each other. Despite exhibiting sequence divergence, CN86 VP6 has 12 out of the 14 residues expected to be conserved in strains bearing subgroup II specificity. Interestingly, CN86 VP6 shows a high degree of homology with VP6 of porcine strain YM rotavirus which, although being closely related to subgroup II strains, has been serologically characterized as subgroup I. Subgroup II reactivity of CN86 strain, predicted by sequence analysis, was confirmed by ELISA with subgroup-specific monoclonal antibodies. Taken together, our results provide evidence for the existence of a human-pig lineage for rotavirus gene 6.

Insulin regulation of glucose turnover and lipid levels in obese children with fasting normoinsulinaemia.

To evaluate the early metabolic alterations induced by obesity, we studied glucose turnover and lipid levels in obese children with fasting normoinsulinaemia. Two experimental protocols were carried out. Protocol I consisted of a euglycaemic glucose clamp at two rates of insulin infusion. Protocol II was similar to protocol I except for a variable lipid infusion used to maintain basal non-esterified fatty acid (NEFA) levels. During protocol I, the glucose disappearance rates were lower in obese children, while no differences were found in hepatic glucose release. NEFA response to insulin was not substantially altered in obese children either at low or high insulin infusion. During protocol II, the NEFA clamp induced a 25% reduction in peripheral insulin sensitivity in control children whereas no changes were observed in obese children. Interestingly, lipid infusion in control children was not sufficient to reproduce the same degree of insulin resistance observed in obese children, suggesting that NEFA are only one of the determinants of insulin resistance at this stage of obesity. In conclusion, the present study provides a portrait of glucose metabolism and lipid levels in normoinsulinaemic obese children. Our results document that peripheral insulin resistance is the first alteration at this stage of obesity, whereas an increase in insulin secretion and a defect in the inhibition of hepatic glucose release by insulin may develop at a later stage. In addition, primarily receptor and post-receptor defects and some alterations of NEFA metabolism are likely to coexist in the induction of insulin resistance at this stage of obesity.

Reproducibility and complications in gene searches: linkage on chromosome 6, heterogeneity, association, and maternal inheritance in juvenile myoclonic epilepsy.

Evidence for genetic influences in epilepsy is strong, but reports identifying specific chromosomal origins of those influences conflict. One early study reported that human leukocyte antigen (HLA) markers were genetically linked to juvenile myoclonic epilepsy (JME); this was confirmed in a later study. Other reports did not find linkage to HLA markers. One found evidence of linkage to markers on chromosome 15, another to markers on chromosome 6, centromeric to HLA. We identified families through a patient with JME and genotyped markers throughout chromosome 6. Linkage analysis assuming equal male-female recombination probabilities showed evidence for linkage (LOD score 2.5), but at a high recombination fraction (theta), suggesting heterogeneity. When linkage analysis was redone to allow independent male-female thetas, the LOD score was significantly higher (4.2) at a male-female theta of.5,.01. Although the overall pattern of LOD scores with respect to male-female theta could not be explained solely by heterogeneity, the presence of heterogeneity and predominantly maternal inheritance of JME might explain it. By analyzing loci between HLA-DP and HLA-DR and stratifying the families on the basis of evidence for or against linkage, we were able to show evidence of heterogeneity within JME and to propose a marker associated with the linked form. These data also suggest that JME may be predominantly maternally inherited and that the HLA-linked form is more likely to occur in families of European origin.

Genome scan of idiopathic generalized epilepsy: evidence for major susceptibility gene and modifying genes influencing the seizure type.

Idiopathic generalized epilepsy (IGE) is a common, complex disease with an almost exclusively genetic etiology but with variable phenotypes. Clinically, IGE can be divided into different syndromes. Varying lines of evidence point to the involvement of several interacting genes in the etiology of IGE. We performed a genome scan in 91 families ascertained through a proband with adolescent-onset IGE. The IGEs included juvenile myoclonic epilepsy (JME), juvenile absence epilepsy (JAE), and epilepsy with generalized tonic clonic seizures (EGTCS). Our linkage results support an oligogenic model for IGE, with strong evidence for a locus common to most IGEs on chromosome 18 (lod score 4.4/5.2 multipoint/two-point) and other loci that may influence specific seizure phenotypes for different IGEs: a previously identified locus on chromosome 6 for JME (lod score 2.5/4.2), a locus on chromosome 8 influencing non-JME forms of IGE (lod score 3.8/2.5), and, more tentatively, two newly discovered loci for absence seizures on chromosome 5 (lod scores 3.8/2.8 and 3.4/1.9). Our data also suggest that the genetic classification of different forms of IGE is likely to cut across the clinical classification of these subforms of IGE. We hypothesize that interactions of different combinations of these loci produce the related heterogeneous phenotypes seen in IGE families.